k, the mouth of the flue, or apron, 3 feet at the front, and 22 inches in the rear.
l, the santee.
m, the fire-arch, with grates at bottom. (This is 22 inches wide at each end, 24 inches in the centre, and 5 feet long from the inside of its mouth to the santee.)
n, the mouth of the fire-arch.
o, the iron pot for the lead to flow into, set in the curve made in the wall for convenience of tapping.
p, the curve in the wall for drawing off the slag.
Figure 4, is a perspective view of the mouth of the flue where the furnace is charged.
From a to b, 6 feet; from a to c, 5 feet; from a to d, 1 foot.
c, the mouth of the flue, 22 inches wide, and 11 high. (This flares out to 3 feet in the distance of 3 feet, the flue covering half of it, so that the heat may be thrown down on the ashes.)
